From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-97546][LOW] xfs: don't spin forever on zero-length dirents when salvaging them Date: Fri, 25 Sep 2026 13:08:53 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-97546 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 0 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 5442f0c56445618544a801fb4dae35aed87a1aaa List-Id: CVE: CVE-2026-97546 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: xfs: don't spin forever on zero-length dirents when salvaging them Commit: 5442f0c56445618544a801fb4dae35aed87a1aaa Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5442f0c56445618544a801fb4dae35aed87a1aaa Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97546 Analysis date: Fri, 25 Sep 2026 13:08:53 -0400 ActionableScore: 0 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97546 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97546 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-97546 LOW https://www.kernelcve.org/list/?q=CVE-2026-97546 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';*CWE-835;*CWE-20;**CWE-400;BEST CVSS score: '1.9';DESCR 'An infinite loop in XFS directory online repair can occur when xrep_dir_recover_data processes corrupted directory metadata containing an unused dirent or normal entry with zero length. The recovery loop does not advance its offset and can consume CPU until the repair operation is terminated. For the CVSS the PR:H reflects that reliably reaching this path normally requires administrative control of XFS online repair and an XFS filesystem with crafted or corrupted on disk metadata. The issue is not network reachable. Impact is limited to local denial of service through a stuck repair task and CPU consumption. No memory corruption or privilege escalation primitive is indicated.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 0) YES DISK SIMPLEFIX LINUS DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_GUESSCVSS YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=0 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=YES NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: -1 * Conservative score: 0 * Raw paranoid score: -1 * Paranoid score: 0 * Final recommended bucket: **Ordinary Moderate**:: The score is clamped to zero because the raw arithmetic is negative. No floor or cap was applied. 2. Signal breakdown * +1 Reliable local CPU consumption. A zero length unused dirent or a normal entry with a zero computed size prevents `offset` from advancing, causing the online directory repair loop to revisit the same metadata indefinitely. * -2 Host-admin-equivalent requirement. XFS online repair is an administrative filesystem operation, and reliably supplying crafted on-disk XFS directory metadata requires control of the filesystem image, backing block device, or equivalent privileged mount and repair environment. Important non-awarded signals: * No UAF, stale reference, double release, refcount mutation, OOB access, or other memory-corruption primitive is established. * No controlled reclaim, arbitrary write, structured object replacement, disclosure, integrity violation, or privilege-escalation path is demonstrated. * No remote reachability is established. The vulnerable loop is reached through local XFS online repair processing. * No additional availability point is awarded. The CPU loop is the same DoS condition already counted above, and `xchk_should_terminate()` is checked in every iteration, allowing the repair operation to be interrupted. * No filesystem ownership or COW security-boundary violation is established. The malformed directory metadata affects repair traversal progress only. 3. Reachability analysis The triggering condition is a corrupted XFS directory block containing a zero length unused dirent or an entry whose computed size is zero. The affected function is in the XFS online directory repair path, not ordinary directory lookup or normal packet or file data processing. A complete reliable trigger normally requires an actor able to run XFS online repair and provide or alter malformed filesystem metadata. This is host-admin-equivalent in the normal XFS deployment model because online repair and control of the mounted filesystem or its backing storage are administrative operations. The complete operation is not namespace-scoped. A user namespace or network namespace does not provide sufficient control over a host XFS mount, its repair interface, and the malformed backing metadata. No special hardware, boot parameter, race condition, or network exposure is involved. 4. Primitive and severity interpretation The exact primitive is a non-advancing loop over malformed directory metadata. When `dup->length` is zero, the old code executes `offset += 0` and continues. When `xfs_dir2_data_entsize()` returns zero, the old code similarly leaves `offset` unchanged. The result is CPU consumption in the XFS repair operation. This is neither active structured-object lifetime corruption nor fixed stale storage. There is no release, free, put, refcount decrement, stale dereference, or second lifetime mutation. It is a validation and loop-progress defect. PrimitiveClass is NONE because the patch establishes no meaningful corruption, ownership, authorization, lifetime, or security-boundary primitive. The demonstrated consequence is a stuck repair task consuming CPU until terminated. A broader host-wide DoS, confidentiality impact, integrity impact, or privilege escalation is speculative and unsupported. ImportantCandidate is NO because this is a constrained administrative repair-path loop with no demonstrated exploitation leverage beyond CPU consumption. AutoDowngradeAllowed is YES because automatic low-priority handling would not discard a concrete unresolved kernel-corruption or boundary-bypass primitive. 5. One-sentence report phrase A malformed zero length XFS directory entry can cause XFS online directory repair to loop without advancing its offset and consume CPU until the repair task is terminated. 6. Manual review recommendation NO MANUAL CHECK NEEDED The patch fixes a bounded-class validation failure in an administrative XFS online repair path. No memory-corruption, authorization, ownership, or privilege-escalation primitive is established. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xfs: don't spin forever on zero-length dirents when salvaging them Commit: 5442f0c56445618544a801fb4dae35aed87a1aaa Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5442f0c56445618544a801fb4dae35aed87a1aaa Commit description: LOLLM noticed that xrep_dir_recover_data can spin forever if it encounters an unused dirent that claims to have length zero. Fix that, and prevent the same thing from happening with a zero-length entry. Cc: stable@vger.kernel.org # v6.10 Fixes: b1991ee ("xfs: online repair of directories") Signed-off-by: Darrick J. Wong Assisted-by: LOLLM # finding obvious bugs Reviewed-by: Christoph Hellwig Signed-off-by: Carlos Maiolino Signed-off-by: Greg Kroah-Hartman Changed files: fs/xfs/scrub/dir_repair.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5442f0c56445618544a801fb4dae35aed87a1aaa ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-97546 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-97546 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: Not available The Best / paranoid CVSS vector: AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L The Best / paranoid CVSS score: 1.9 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: unknown Paranoid ActionableScore: 0 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).